An industrial robot is used as a manipulator for carrying out a handling operation such as gripping, transferring, or positioning a work piece by an end effector such as a robot hand equipped at an end of a robot arm, in accordance with a programmed command or a teaching command. A movable element such as the robot arm is sometimes positioned at a constant level with regard to the attachment thereof to the robot, and the movable element itself is driven by the drive motor. On the other hand, a robot having the following operational function is in use, in which a vertically movable element itself is moved vertically by an operational mechanism for a vertical motion having a vertically extended ball screw shaft, so that a tip end of the movable element is moved vertically toward or away from a work piece.
FIG. 5 is a perspective and schematic view of a supporter for supporting a vertically extended shaft such as the above-mentioned ball screw shaft, but does not show the vertically extended shaft. The supporter comprises a base 1 for the vertically extended shaft, two shafts 2 and a supporting member 3 projecting upward from a plate 1a of the base 1, and an upper plate 4 mounted on the tops of the shafts 2 and the supporting member 3. Furthermore, the base 1 comprises a gear box 5 at one end thereof. A lower end of a ball screw shaft, not shown, is rotatably journaled at a substantially central position of the plate 1a of the base 1, and an upper end thereof is journaled by a bearing on the upper plate 4. In general, the gear box 5 is molded as one body with the base 1 to reduce the number of steps required for assembling such a supporter for supporting a vertically extended shaft, and the above-mentioned shafts 2 and supporting member 3 are welded to the base 1 to form a one-body type supporter.
A drive motor (not shown) for driving the above-mentioned ball screwshaft is attached to the gear box protruding from the above-mentioned one body type supporter to facilitate the maintenance thereof after attachment, and rotates the ball screw shaft via a reduction mechanism, i.e., gears housed in the gear box 5, and not shown belts and pulleys provided in the above-mentioned base 1.
The above-mentioned supporter, however, is not compact because the gear box 5 thereof protrudes outward, and in particular, it is difficult to adapt same to a robot having an elongated body along the axis of a ball screw shaft.